Spatial light modulator using an integrated circuit actuator and method of making and using same

ABSTRACT

A spatial light modulator (SLM) includes an integrated circuit actuator that can be fabricated using photolithography or other similar techniques. The actuator includes actuator elements, which can be made from piezoelectric materials. An electrode array is coupled to opposite walls of each of the actuator elements is an electrode array. Each array of electrodes can have one or more electrode sections. The array of reflective devices forms the SLM.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to spatial light modulators, and moreparticularly, to reflective spatial light modulators.

2. Background Art

A spatial light modulator (SLM) (e.g., a digital micro mirror device(DMD), a liquid crystal display (LCD), or the like) typically includesan array of active areas (e.g., mirrors or transmissive areas) that arecontrolled to be either ON or OFF to form a desired pattern. Apredetermined and previously stored algorithm based on a desiredexposure pattern is used to turn ON and OFF the active areas.

Conventional reflective SLMs use mirrors (e.g., reflective elements,pixels, etc.) as the active areas. The mirrors are controlled usingelectrical circuits that cause resilient devices (e.g., leverage arms)to tilt or move the mirrors. For example, electrostatic tilting mirrorscan be used. The tiling or moving cause light transmitted towards themirrors to be reflected towards or away from a target. SLMs haveincluded increasingly smaller mirrors in recent years to comply with theincreasing resolution required of them. However, further decrease in thesize of the mirrors is limited based on the current manufacturingtechnology and materials used. For example, current mirrors can be assmall as about 16 microns in width or diameter. Example environmentsusing an SLM can be photolithography, maskless photolithography,biotechnology, projection televisions, and the like.

Lithography is a process used to create features on the surface ofsubstrates. Such substrates can include those used in the manufacture offlat panel displays (e.g., liquid crystal displays), circuit boards,various integrated circuits, and the like. A frequently used substratefor such applications is a semiconductor wafer or glass substrate. Whilethis description is written in terms of a semiconductor wafer or a flatpanel display, for illustrative purposes, one skilled in the art wouldrecognize that this description also applies to other types ofsubstrates known to those skilled in the art.

During lithography, a wafer, which is disposed on a wafer stage, isexposed to an image projected onto the surface of the wafer by exposureoptics located within a lithography apparatus. While exposure optics areused in the case of photolithography, a different type of exposureapparatus can be used depending on the particular application. Forexample, x-ray, ion, electron, or photon lithography each can require adifferent exposure apparatus, as is known to those skilled in the art.The particular example of photolithography is discussed here forillustrative purposes only.

The projected image produces changes in the characteristics of a layer,for example photoresist, deposited on the surface of the wafer. Thesechanges correspond to the features projected onto the wafer duringexposure. Subsequent to exposure, the layer can be etched to produce apatterned layer. The pattern corresponds to those features projectedonto the wafer during exposure. This patterned layer is then used toremove or further process exposed portions of underlying structurallayers within the wafer, such as conductive, semiconductive, orinsulative layers. This process is then repeated, together with othersteps, until the desired features have been formed on the surface, or invarious layers, of the wafer.

Step-and-scan technology works in conjunction with a projection opticssystem that has a narrow imaging slot. Rather than expose the entirewafer at one time, individual fields are scanned onto the wafer one at atime. This is accomplished by moving the wafer and reticlesimultaneously such that the imaging slot is moved across the fieldduring the scan. The wafer stage must then be asynchronously steppedbetween field exposures to allow multiple copies of the reticle patternto be exposed over the wafer surface. In this manner, the quality of theimage projected onto the wafer is maximized.

Conventional lithographic systems and methods form images on asemiconductor wafer. The system typically has a lithographic chamberthat is designed to contain an apparatus that performs the process ofimage formation on the semiconductor wafer. The chamber can be designedto have different gas mixtures and/or grades of vacuum depending on thewavelength of light being used. A reticle is positioned inside thechamber. A beam of light is passed from an illumination source (locatedoutside the system) through an optical system, an image outline on thereticle, and a second optical system before interacting with asemiconductor wafer.

A plurality of reticles is required to fabricate a device on thesubstrate. These reticles are becoming increasingly costly and timeconsuming to manufacture due to the feature sizes and the exactingtolerances required for small feature sizes. Also, a reticle can only beused for a certain period of time before being worn out. Further costsare routinely incurred if a reticle is not within a certain tolerance orwhen the reticle is damaged. Thus, the manufacture of wafers usingreticles is becoming increasingly, and possibly prohibitively,expensive.

In order to overcome these drawbacks, maskless (e.g., direct write,digital, etc.) lithography systems have been developed. The masklesssystem replaces a reticle with a SLM. However, as feature sizes becomesmaller, conventional SLMs may no longer provide the required resolutionneeded.

Therefore, what is needed is a system and method providing an SLM thatcan be used for very high resolution environments.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide an integrated circuitmicro-optoelectro-mechanical system (MOEMS) spatial light modulatorincluding an array of reflective devices, an integrated circuit actuatorhaving an array of actuator elements, first and second arrays ofelectrodes coupled to opposite walls of each of the actuator elements.Electrical energy can cause the actuator material (e.g., piezoelectricmaterial) to expand or contract, which moves the reflecting devices in acorresponding direction.

A still further embodiment of the present invention provides a methodincluding the following steps. Transmitting light towards a MOEMSintegrated circuit spatial light modulator having an array of mirrors.Moving the mirrors using integrated circuit actuators via electrodescoupled thereto. Forming a wavefront based on the light interacting withthe mirrors.

Further embodiments, features, and advantages of the present inventions,as well as the structure and operation of the various embodiments of thepresent invention, are described in detail below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention.

FIG. 1 shows a portion of an SLM according to embodiments of the presentinvention.

FIG. 2 shows a portion of an SLM according to embodiments of the presentinvention.

FIG. 3 shows a portion of an SLM according to embodiments of the presentinvention.

FIG. 4 shows a flowchart depicting a method for making an SLM accordingto embodiments of the present invention.

FIG. 5 shows a flowchart showing details of steps performed in FIG. 4according to one embodiment of the present invention.

FIGS. 6, 7, and 8 show various electrode patterns according to variousembodiments of the present invention.

FIG. 9 shows a portion of an SLM according to embodiments of the presentinvention.

The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers mayindicate identical or functionally similar elements. Additionally, theleft-most digit(s) of a reference number may identify the drawing inwhich the reference number first appears.

DETAILED DESCRIPTION OF THE INVENTION

Overview

While specific configurations and arrangements are discussed, it shouldbe understood that this is done for illustrative purposes only. A personskilled in the pertinent art will recognize that other configurationsand arrangements can be used without departing from the spirit and scopeof the present invention. It will be apparent to a person skilled in thepertinent art that this invention can also be employed in a variety ofother applications.

Embodiments of the present invention provide a MOEMS or MEMS SLM thatincludes an integrated circuit actuator that can be fabricated usingphotolithography or other similar techniques. The actuator includesactuator elements, which can be made from piezoelectric materials. Firstand second electrode arrays are coupled to opposite walls of theactuator elements to provide power thereto. Each array of electrodes canhave one or more electrode sections. The array of reflective devicesforms the mirror of the SLM and are moved via the actuator elementsbased on the electrical energy being provided to the electrodes.

In one example environment, the SLM can be used in place of a reticle inmaskless photolithography to project patterns onto a substrate. Inanother example, the SLM can be used in a projection optical system of aphotolithographic tool, if the SLM is aspherical in shape, to correctfor aberrations in a wavefront. In yet another example, the SLM can beused in biomedical and other biotechnology environments, as is known inthe relative arts. In yet still another embodiment, the SLM can be usedin projection televisions. In other examples, using the fine resolutionaccomplished through the integrated circuit actuators, the SLM can fix asigma during pupil fill and can be part of a dynamically adjustable slitapplication to correct illumination uniformity. The are all exemplaryenvironments, and are not meant to be limiting.

Two-Directional Movement Actuators

FIG. 1 shows a portion of an SLM 100 according to embodiments of thepresent invention. In various embodiments, SLM 100 can be an integratedcircuit micro-optoelectro-mechanical system (MOEMS) SLM ormicro-electro-mechanical system (MEMS) SLM. SLM 100 includes a substrate102 having an optional thermally insulating layer 104. An array ofelectrodes 106 can be coupled to insulating layer 104 or substrate 102.Actuator elements 108 are coupled between electrodes 106 and anotherarray of electrodes 110. Reflective devices 112 are coupled to the arrayof electrodes 110. In this configuration, actuator elements 108 can movereflective devices 112 in two directions (e.g., up and down) when beingenergized via electrode 106. This

-   -   can be referred to as a piston-like motion. In one embodiment,        the distance of movement can be +/−¼λ, where λ is a wavelength        of impinging light (not shown). In other embodiments, the        distance may be smaller, such as ⅛ or {fraction (1/16)}λ, or any        other.

Although not specifically shown, electrodes 106 can be coupled toconductive devices (e.g., wires) coupling electrodes 106 to a controlleror a power supply. The wire can either pass through substrate 102 or bedirectly coupled to electrodes 106. Layout and fabrication of such wireinterconnects are well known in the manufacturer manufacturing art.

Each actuator element 108 can be made using piezoelectric materials. Forexample, lead zirconate titanate (PZT), zinc oxide (ZnO), polyvinylidenefluoride (PVDF) polymer films, or the like can be used (hereinafter, theterm piezoelectric and all materials that can make up the same will bereferred to as “PZT”).

The integrated circuit actuator elements 108 work in a linear fashion,which provides phase shift and creates interference patterns to providefiner resolution. Also, manufacture of the integrated circuit actuatorelements 108 is simpler compared to conventional actuators becauseintegrated circuit actuators do not require electrostatic and complexlithography techniques during formation.

Depending on a height (e.g., thickness) of each actuator element 108and/or spacing between actuator elements 108, each actuator element 108can be decoupled or coupled to each other actuator element 108, forexample as discussed below with reference to FIGS. 2-3. This can bebased on a desired use of SLM 100.

FIG. 9 shows a portion of an SLM 900 according to embodiments of thepresent invention. In this embodiment, actuator elements 108 can havevarying heights in order to form an overall curved, convex, spherical,aspherical, etc. shaped SLM 900. It is to be appreciated that a concaveshape can also be formed. Also, actuators elements 108 can be placed invarious locations on substrate 102. Varying one or both of height and/orposition of the array of actuator elements 108 can allow for variousdiffraction patterns to be formed by reflective devices 112.

With reference again to FIG. 1, and continuing reference to FIG. 9,reflective devices 112 can be configured to form various shapes, e.g.rectangular, circular, quasar shaped, aspheric, etc. Reflective devices112 can be made from silicon, gallium arsinide, gallium nitride, glass,or the like. Integrated circuit actuator configurations and/or sizes canbe tailored to provide the desired response at the mirror and can be useduring a high frequency operation (e.g., 50-100 kHz).

FIG. 2 shows a portion of an SLM 200 according to embodiments of thepresent invention. SLM 200 is similar in operation and make-up to SLM100, except that it includes a piezoelectric structure 202 betweenactuator elements 108 and electrodes 106 and a conductive structure 204between actuator elements 108 and electrodes 110. These structures 202and 204 can allow adjacent actuator elements 108 to be coupled (e.g.,controlled) together, allowing control of a group of reflective elements112 at a time. It is to be appreciated that specific shapes and/or sizesof structures 202 and 204 can vary based on implementation specificdesign requirements.

In other embodiments (not shown), the bottom electrode layer can be asingle electrode across the bottom or rows of electrodes, rather thanindividual electrodes 106. This can be used to minimize the number ofelectrical connections. Insulator layer 104, or portions thereof, can beomitted. A single control line would be coupled to electrode array 110and not the single electrode.

Four-Directional Movement Actuators

FIG. 3 shows a portion of an SLM 300 according to embodiments of thepresent invention. SLM 300 is similar to SLMs 100 and 200, except thateach electrode 106 includes two sections 106A and 106B, which areindependently controlled. Actuator elements 108 can move reflectivedevices 112 in four directions (e.g., up, down, tilt left, tilt right)based on using the two electrode sections 106A and 106B. Only energizingone electrode section 106A or 106B at a time accomplishes this. Forexample, energizing electrode section 106A will cause actuator element108 to tilt down left or up right (in the perspective shown), which inturn causes reflective device 112 to move in the same direction. Theopposite is true when energizing electrode 106B.

It is to be appreciated that closed loop position control can be used tocontrol SLMs 100, 200, or 300. Each actuator element 108 can be used tomeasure capacitance, since each PZT is basically an insulator. Measuringthe capacitance change can predict how much actuator element 108, and inturn reflective element 112, has moved. This can be used to confirm themovement taking place.

Also, since PZT devices have hysteresis. If SLM 100, 200, or 300 followsa predetermined algorithm and repeats it, each actuator element 108, andin turn each reflective device 112, can have repeatable positions. Usinga proper algorithm can reset the PZT material every time it is moved, sothat positions can repeat quite accurately. Method for Making an SLMwith an Integrated Circuit Actuator

The following is one example process 400 that can be used to form SLM100 or 900. It is to be appreciated many other processes used to formintegrated circuits that are now know or developed in the future arealso contemplated within the scope of the present invention.

FIG. 4 shows a flowchart depicting a method 400 according to anembodiments of the present invention. In step 402, a conductiveinterconnect pattern is formed on a substrate. In step 404, a pluralityof piezoelectric elements are formed on the conductive interconnectpattern. In step 406, respective electrodes are formed on an end of theplurality of piezoelectric elements. In step 408, mirrors are formed onthe electrodes on the ends of the piezoelectric elements.

FIG. 5 shows a flowchart showing details of steps performed in method400 according to an embodiment of the present invention (steps 502-522).

In step 502, which is related to step 402, substrate 102 (e.g., silicon,sapphire, and silicon on sapphire, etc.) is plated with an interconnectpattern using a suitable conductor (e.g., nickel, etc.) to provideelectrodes 106 (e.g., individual ohmic connections to the PZT layer 108to be formed later).

In step 504, which is related to step 404, a film of PZT material 108can be formed using deposition, sputtering, evaporation, plating, or anyother know or future developed process. A layer several microns thickmay be needed depending upon a specific application of SLM 100.

In step 506, which is related to step 406, a top conductor layer 110 canbe formed to provide ground plane connections for PZT actuator 108.

Steps 508 to 518 are related to step 408.

In step 508, materials used to form reflective devices 112 can beapplied. In step 510, the material for the reflective devices 112 can becoated, for example, with resist that is subsequently exposed in step512 with a reflector pattern. In step 514, the resist can be developed.In step 516, the mirror layer areas can be exposed to be etched.Reflector size can be selected to have a single PZT actuator 108 perreflector 112.

In one embodiment, an anisotropic etching technique can be used to etchthrough unmasked areas of the reflective device/PZT layer. This willform mirror/actuator arrays, while substantially reducing actuatorunderetching. Examples of such techniques can include chemicallyassisted plasma etching techniques, sputter techniques, ion milling,etc. In another embodiment, laser ablation can be used to separatereflective device/PZT elements.

In step 518, the remaining resist can be removed.

Steps 520-522 are optional steps not specifically shown in FIG. 4.

In step 520, a lapping operation can be performed to provide a flatsurface with an actuator pattern thereon.

In step 522, SLM 100 can be packaged and/or bonded.

It is to be appreciated that actuator elements 108 can be formed usingother equivalent process steps and/or other orders of process steps, aswould be known to one of ordinary skill in the relevant arts.

In one embodiment, actuator elements and the associated reflectivedevices can have diameters or widths of as small as about 1 micron,which is magnitudes smaller than the conventional actuators that cantypically only be as small as about 16 microns. This is accomplishedthrough using the integrated circuit manufacturing techniques (e.g.,photolithographic techniques) described above. It is to be appreciatedthat even smaller diameters or widths are possible for the actuatorelements and/or mirrors as integrated circuit technology advances. Thus,a very high resolution SLM can be manufactured that is able to be usedin very small wavelength environments (e.g., EUV). It is to beappreciated that the ranges for mirror size and density may change inthe future as technology advances, and are not meant to be limiting,only exemplary.

Electrode Patterns

FIGS. 6-8 show various electrode patterns according to variousembodiments of the present invention. Depending on an application of SLM100 and/or a coordinate system used to control SLM 100, variouselectrode patterns can be used. The electrode pattern used will dictatethe number of degrees of freedom for SLM 100. It is to be appreciatedthat the electrode patterns shown in these figures and discussed aboveare merely exemplary, and not meant to be exhaustive. Other electrodepatterns can be used, and are contemplated within the scope of thepresent invention. For example, an number and any placement ofelectrodes can be used to provide any desired location of an axis ofrotation or axes of rotation. This is all a result of using integratedcircuit actuators.

FIG. 6 is a top view of a pattern 600 of either first electrode array106 or second electrode array 110 on actuator elements 108. Pattern 600allows SLM 100 to rotate or pivot about four axes.

FIG. 7 is a top view of a pattern 700 of either first electrode array106 or second electrode array 110 on actuator elements 108. Pattern 700allows SLM 100 to rotate or pivot about one axis.

FIG. 8 is a side-view of a section of SLM 100 according to embodimentsof the present invention. In this configuration, in addition to firstand second electrode arrays 106 and 110, a third electrode array 800 anda fourth electrode array 802 are coupled/deposited to actuator elements108. This can allow for X, Y, and Z motion for the actuator elements 108and respective reflective devices 112. Therefore, mirrors 112 can“shift” or be displaced side to side (in the perspective of the figure)when electrodes 800/802 are energized. It is to be appreciated that onlyone pair of electrodes, 106/110 or 800/802, can be coupled to oppositewalls of the actuator elements 108.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A integrated circuit spatial light modulators comprising: reflectivedevices; a solid and substantially rigid substrate; and an actuatorcomprising actuator elements and first and second sets of electrodes,wherein respective electrodes in the first set of electrodes are coupledto a first portion of respective ones of the actuator elements and arecoupled to respective ones of the reflective devices, and whereinrespective electrodes in the second set of electrodes are coupled to asecond portion of the respective ones of the actuator elements and arecoupled to the solid and substantially rigid substrate.
 2. The spatiallight modulator of claim 1, wherein the actuator elements and electrodesare configured to move the reflective devices in two directions.
 3. Thespatial light modulator of claim 1, wherein the actuator elements andelectrodes are configured to move the reflective devices in fourdirections.
 4. The spatial light modulator of claim 1, wherein eachelectrode in the second set of electrodes comprises first and secondelectrode sections.
 5. The spatial light modulator of claim 4, whereinthe first and second electrode sections and the first set of electrodesare configured to allow the actuator elements to tilt the reflectivedevices.
 6. The spatial light modulator of claim 1, further comprising:a first coupling device between the actuator elements and electrodes inthe second set of electrodes; and a second coupling device betweenelectrodes in the first set of electrodes.
 7. The spatial lightmodulator of claim 1, wherein adjacent ones of the actuator elementshave different heights.
 8. The system of claim 2, wherein the actuatorelement moves the reflecting device about one-quarter of a wavelength oflight in each direction.
 9. (cancelled)
 10. The spatial light modulatorof claim 1, wherein the actuator elements are configured such that thereflective devices form an overall curved shape.
 11. The spatial lightmodulator of claim 1, wherein the actuator elements are formed invarying heights and positions on the solid and substantially rigidsubstrate, such that varying wavefront patterns are generated by lightreflecting therefrom. 12-26. (canceled).
 27. The system of claim 3,wherein the actuator elements move the reflecting device aboutone-quarter of a wavelength of light in each direction.
 28. (cancelled)